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Too cold for people, but not for plants

February 27, 2014

Hydrangeas and other plants are not harmed by a blanket of snow.

A cold, shivery winter like this one often makes gardeners worry about their plants. But in fact, plants probably suffer less than people, says Doris Taylor, Plant Clinic manager at The Morton Arboretum.

Most of the species that we plant in our gardens are evolved for cold climates and are safely dormant in winter. And though a deep layer of snow may be a pain in the neck for drivers, for plants it’s a cozy comforter. 

“Snow is excellent insulation,” Taylor says. “It actually protects the plants’ roots from the bitter cold.” Perennials and bulbs that were safely under the snow should be fine, and the melting snow will give them a good start in spring.

Some needles on evergreens or twigs on trees and shrubs that aren’t insulated by snow may die back from drying winter winds and turn brown. But before pruning, wait a bit to make sure they won’t recover and green up or leaf out when they get a good drink in spring. If twigs or needles do turn out to be dead, just prune them out to let the plant fill in.

In winter, plants can easily be harmed by the things we do to cope with snow.

For example, shrub and tree branches can break when we try to shake snow off, which usually isn’t necessary. A heavy load of snow that bends down evergreens’ branches and sometimes even their trunks can be alarming to look at. Shaking or sweeping branches is especially hazardous if the snowfall has been followed by bitter cold, as it can make branches especially brittle. But in most cases, Taylor says, the trees will return to shape when the snow melts.

Heavy snow can snap branches on a few kinds of evergreens with upward-pointing branches, such as arborvitaes. It’s okay to gently shake or brush snow off those plans while it’s falling to keep it from building up. But if you wait until the snowfall is done and branches are heavily burdened, it’s best to leave them alone and let the snow melt.

Another way we make the situation worse for plants is by spreading too much salt. Salt and other melting products can dry out and damage plants’ roots and stems. Use only what you need for safety and not as a substitute for shoveling.

When you do shovel, try to avoid dumping snow contaminated with melting products at the base of trees or onto beds and lawns, where salt from melted snow will end up in the plants’ root zones. It’s better to shovel snow onto a hardscape area such as a patio.